Your code is useful! could you please include a permissive license?

[faustomilletari]

Dear Kuangliu,

it's great to see your work. A lot of people are using your code for their free and open source projects, which is also great.

It would be nice if you could add a license to this repo (Eg. MIT license which is very permissive and won't force us to change our licenses) so that we can 1) link your repo from other code (which is something most people already do) and 2) be sure we won't have legal issue due to lack of license for using the code.

Thanks!